Neuromodulation, also referred to as neurostimulation, has been proposed as a therapy for a number of conditions. Examples of neuromodulation include Spinal Cord Stimulation (SCS), Deep Brain Stimulation (DBS), Peripheral Nerve Stimulation (PNS), and Functional Electrical Stimulation (FES). For example, SCS has been used to treat chronic pain syndromes. Some neural targets may be complex structures with different types of nerve fibers. An example of such a complex structure is the neuronal elements in and around the spinal cord targeted by SCS.
Implantable neuromodulation systems have been applied to deliver such a therapy. An implantable neuromodulation system may include an implantable neuromodulator, also referred to as an implantable pulse generator (IPG), and one or more implantable leads each including one or more electrodes. The implantable neuromodulator delivers neuromodulation energy through one or more electrodes placed on or near a target site in the nervous system. An external programming device may be used to program the implantable neuromodulator with stimulation parameters controlling the delivery of the neuromodulation energy.
Electrical stimulation energy may be delivered from the implantable neuromodulator to the electrodes to stimulate neural tissue in the form of an electrical pulsed waveform. The configuration of electrodes used to deliver electrical pulses to the targeted tissue constitutes an electrode configuration, with the electrodes capable of being selectively programmed to act as anodes (positive), cathodes (negative), or left off (zero). In other words, an electrode configuration represents the polarity being positive, negative, or zero. Other parameters that may be controlled or varied include the amplitude, pulse width, and rate (or frequency) of the electrical pulses provided through the electrode array. Each electrode configuration, along with the electrical pulse parameters, constitutes a modulation parameter set for use in an electrostimulation therapy.